It is known that fluctuation of brightness, which is called flicker, is generated in an image that is captured under illumination light, such as a fluorescent lamp, whose brightness cyclically fluctuates, for example. The flicker is generated when a cycle in which an image sensor generates an image differs from a fluctuation cycle of a brightness of an object. For example, when a moving image is captured at a predetermined frame rate, and the frame rate differs from a frequency of illumination light, the brightness of the image can differ between frames. Also, when an image sensor employs a rolling shutter method or the like, and the timing of light exposure differs for each position in a captured image, the brightness of the image cyclically changes in the same frame (thereby, a stripe pattern is generated in the image, for example). The flicker in the captured image is an obstacle in improving the quality of the captured image, and thus various technologies for removing this are proposed. An example of such technologies is described in Patent Literature 1.